dspic33

We love a good line-following robot project and this really hits the spot. It’s got sharp edges, gobs of solder bridging, and look at all those jumper wires! Despite its appearance it puts in a performance that won’t disappoint.

It uses a dsPIC33 to read from half a dozen analog sensors on the bottom of the board. We’re not all that familiar with the chip’s features, but [Exapod] says it’s got an auto-scan feature he uses to read the sensors. This allows him to sample with 12-bit resolution from all six of them at about 30 kHz. No wonder the thing is so responsive in the demo video embedded below. The track he’s using is just some white printer paper with a fat circuit of black electrical tape placed in a somewhat squiggly pattern.

The good [Doctor Iguana] has been working on a pair of robots which communicate with each other using mRF24J40MA wireless transceivers. This presents a challenge in debugging, as he really didn’t have an easy way of monitoring those communications. His solution was to build his own base station which lets him use a computer to monitor what each robot is saying.

He spun his own board for the project. USB connectivity is provided by an FTDI chip, the FT232RL. This converts the USB communications in to serial for the dsPIC33 microcontroller. The FTDI chip comes with a fairly fine-pitch, but the footprint can still be fabricated using toner transfer if you’re fairly familiar with the process. [Dr. Iguana] took some close-up images of the unpopulated board which might make you a little nervous with the soldering iron. The other end of the board hosts the same Microchip wireless module as he used in his robots.

After a bit of rework (noted on the photo labels) he got this up and running. Now he can capture all of the wireless communications and see if problems are due to the sender or the receiver.

As with the reference design, his board uses a dsPIC33. But instead of using a series of discrete MOSFETS to switch the signals to the motor, he sourced an L298N motor driver. That’s it sticking up next to the large capacitor. When driven hard it needs its own heat sink, which [Uwe] cut from a larger CPU heat sink. During development, he decided to use interrupt-based PWM rather than the hardware PWM offered by the dsPIC. It works, but he would go the other route if doing it again.

For the pedestrian, the video after the break has all the details you need. For those that really want to dive in, [Uwe’s] multi-paged write-up is worth bookmarking.

[ESylin] built an autonomous rover that roams the vacant halls of his school. On the hood of the vehicle he’s mounted two Maxbotix sonar sensors that do a great job of keeping the vehicle centered in the hallway. It will follow a wall around a corner (favoring its left side because of the left-facing sensor) and it will stop to correct itself if it gets off course. That’s because when you’re not driving a dsPIC33 is, with a Traxxas XL-5 speed controller and a hobby servo for steering. But this little guy hasn’t lost all his pep. Manual control and be switched on from from an R/C controller so you can burn up the floor tiles. Take a look at the demo after the break, with the manual control demo shown at about 4:10. Continue reading “Autonomous rover roams the halls”→